DE3427994A1 - AXIAL COMPACT DIRECT DRIVE MOTOR - Google Patents

Abstract

Signal processing units are more and more widely used as portable apparatuses or susceptible of being installed in very compact units. It is therefore necessary to obtain a face-to-face dimension which is further reduced and a decrease of the cost of the drive mechanisms. These problems are solved by fixing the shield ring (30) to the plate support (31) by adhesion (86) and by simultaneously fitting and cutting a plurality of finished units (30, 31). The invention may be used in the field of drive mechanisms for hard or flexible disk memories of video units and record players.

Description

Axially compact direct drive motor for driving signal

processing devices The invention relates to an axially compact Direct drive motor according to the preamble of claim 1. In such drives, those for the direct drive of so-called hard disk drives or Winchester Drives One or more disks, but also for driving so-called floppies or video drives or turntables or optical disks are suitable, There is increasing demand for an economically inexpensive mass-produced product axial compactness on the market.

The invention is therefore based on the object of a generic Motor to achieve a large axial compactness in a simple manner, or existing To improve drives in this direction. Especially with the small size of this one specified dimensions with air gap diameters of approx. 50 mm or less and axial laminated core lengths of the stator of a few millimeters often results in In practice, a battle for millimeters and low manufacturing costs in series production.

The object is preferably achieved with the means of claim 1.

The advantages of the invention and further developments are combined will be described in detail below with the figures.

1 shows a first exemplary embodiment of the invention in FIG Section on a scale of 2: 1; Fig. 2 shows a composite board of a direct drive motor in Top view for an engine according to FIG. 1 or FIG. 5; Fig. 3 along a section the line III-III; 4A shows an intermediate state in the manufacture of the composite board according to FIG. 2; FIG. 4B shows a multiplicity of units according to FIG. 4A in a large-area Composite panel; 5 shows a second, axially even more compact embodiment, similar As in FIG. 1, but with an adjustable Hall generator, on a scale of 2: 1; 6 shows a circuit example for the evaluation of a pulse; 7A shows the planar development of the rotor magnets according to FIG. 8; 78 shows the induction curve 8 at the Hall generator when the Rotor magnets according to arrow 107 in FIG. 7A (or 8); 7C shows the one above the air gap area flux summed up in the direction of the circumferential angle f (area integral B over P); 8 top view of the open end face of the rotor bell according to FIG. 1 or FIG. 5 (natural size!).

In Fig. 1, a brushless DC motor is constructed External rotor direct drive motor for magnetic hard disk storage illustrates which is designated as a whole by 10. The motor has a cup-shaped rotor housing 11, which sits concentrically to a rotor shaft 12 and with this via a socket 13 is firmly connected, which is pressed into a central opening of the rotor housing. In the made of magnetically highly conductive material rotor housing 11 are a A plurality of permanent magnet pieces or a one-piece permanent magnet 14 attached, which, together with the components 11 to 13, forms the rotor 15 of the motor 10. Of the Permanent magnet ring 14 is preferably made from a mixture of hard ferrite, e.g. Barium ferrite, and elastic material.

So it is a so-called rubber magnet. pieser is trapezoidal or approximately trapezoidal over the pole pitch with a relatively small pole gap, for example four-pole radially magnetized, so that on the inside of the permanent magnet 14 facing the cylindrical air gap 16 in alternating the sequence two mechanical north dololes and two mechanical south polev are available, each about 900th in width. The rotor housing 11 can be produced as a deep-drawn part. It represents a magnetic return path. In the corner area, which is formed by the bottom 17 of the rotor housing 11 and the inner circumference of the permanent magnet 14, a cube-shaped index magnet 18, for example, is attached to a predetermined location with respect to the magnetization of the permanent magnet 14, for example in the Rotor housing 11 glued in place.

A magnetic field sensor 41 is also attached to the circuit board carrier 31, which is a Hall generator, which is in a small axial distance from the bottom 17 of the housing pot 11 with a permanent magnet 14 large radial air gap 114 and to the index magnet 18 small radial air gap 118 lies.

The type of assembly of the index magnet 18 illustrated in FIG. 1 and that with the permanent magnet 14 and the index magnet to form a radial one Air gap cooperating Hall generator 41 has particular advantages in that when the Hall generator 41 is effectively exposed to the field of the magnets 14, 18, from the stray field of the coil heads incident at a different angle of action 22 is only minimally affected. The rotor 15 can be withdrawn from the stator 20, or place it on the stator without the index magnet 18 being in the way. the axial overall height of the motor 10 is particularly low. It is understood that the present did not disclose type of attachment of the index magnet and the magnetic field sensor on a specific design of the commutation signal and / or the index signal generator stage is limited.

However, the arrangement according to FIG. 1 shows not only one in view on the stray field influence from the stator advantageous effect, but this arrangement has in connection with the fact that the permanent magnet 14 is a ceramic magnet with a relatively high remanent induction of 4-5 KG (KiloGaus) is another advantageous one Effect. If you have the index magnet 18, which is a samarium cobalt magnet (SmCo) with a high remanent induction of 8-10 KG is, for reasons of cost extremely small in connection with the "motor" magnet huge Volume (permanent magnet 14) used in its vicinity for index pulse generation, is obtained despite the relatively high permanent induction of the index magnet 18, but because of its extremely small size, it does not have a clean impulse, since the The effect of the field of the magnets 14 and 18 on the Hall generator 41 is superimposed and thereby the impulse is "smeared". Despite this overlay, the Index magnet 18 cause a sharp pulse in Hall generator 41. In the illustrated Arrangement of a radially small air gap 118 between the radially magnetized Index magnet 18 and the Hall generator 41 and one radial to it for comparison Multiple larger radial air gap 114 between the Hall generator 41 and the also radially magnetized magnet 14 ("main magnet" or "motor magnet") now this overpowering, smudging influence, softening the sharp impulse of the main magnet 14 is reduced.

Since the Hall generator 41 is simultaneously in a 5tornut (including its Halterun§3v) is cleverly arranged, but which has a relatively large groove opening has (thus again not the permanent magnetic field acting on the Hall generator too much is absorbed by the pole ends on both sides of the slot, so that the slot opening forms a sufficiently large "magnetic window" for the Hall generator 41), one achieves an optimal constellation with great compactness in the axial and radial direction Direction between motor magnet 14, index magnet 18, Hall generator 41, coil head 22, Stator laminated core 21.

The different radial air gaps 118 and 114 are just effective the ideal combinability of such a doubly used Hall generator 41, which not only provides an index signal, but also a rotor position signal for commutation the stator winding together.

If the permanent magnet 14 were a so-called plastic-bonded magnet (rubber magnet), then it would have a relatively low remanent induction and the impulse of the magnet 18 would still be sufficiently sharp in relation to the rotor field lifted off - have a sufficient steepness, even if the position is in the area of the other axial end of the air gap. But if you want to use ceramic magnets, as here, this arrangement according to FIG. 1 is, so to speak, "impulsive" and optimal for compactness, at the same time also for assembly. In addition, as mentioned, the stray field influence from the stator is smaller than if the index magnet were arranged in the area of the open end of the housing pot 11.

The free space 116 radially between the index magnet 18 and the cylinder wall of the housing pot 11 also acts at that point in the sense of a relative Reinforcement of the index field, also in the sense of an improvement of the impulse. For this purpose, the axial length of this free space 116 should even be greater (definitely twice as large as drawn in Fig. 1) It is just about the optimal Dimensioning of these ratios in the inner corner of the housing pot 11 between Permanent magnet 14, index magnet 18, Hall generator 41 and stator laminated core 21 expressly referred to the drawing proportions! The free space 116 can for manufacturing reasons in any case cannot be completely filled with the magnetic material, even if the stator laminated core axially would be a little longer (despite the necessary axial maximum motor dimension), so that this arrangement really forms a very advantageous solution overall.

The radially very large air gap of space 116 adds up, so to speak to the already existing large air gap 114, so that the influence of the motor magnet on the Hall generator 41 is therefore even more "subtle" overall.

FIG. 2 shows the top view of a finished, equipped composite board 87 provided with connection licenses 83 in the installed state according to FIG. 5 from below, however, in front of their Montaoe. the Plate is equipped with electronic components 84, 85ClOipg.

This is a low-cost, automatable assembly method in the sense of axial compactness. The Hall generator support 81 is angled Plastic part formed, as Fig. 3 shows in detail. He's injected over a Plastic rivet head 85 fastened in the composite plate 87 in a hot, twisted manner. The angled Element 81 carries the Hall generator 41 at the upper end, its right end face points towards the radial air gap. The angled element is resilient in the direction of angling designed so that the worm screw 82 used by adjustment and support on the composite board 8} the angular position of the Hall generator or of the carrier 81 changed to the flat surface of the part 87. In some cases this adjustment is very desirable, because you can still adjust the signal sensitivity with it. The screw 82 is Can also be adjusted with the fully assembled inner stator, but before the rotor pot is put on. The adjustment can also still be traced, if it is in the bottom of the rotor pot 11 is an opening at the appropriate radial distance from the shaft, so that this opening with the corresponding circumferential position of the rotor above the screw head the worm screw 82 may be located. Advantageously, however, the adjustment is made before made the placement of the rotor with the help of an adjustment device.

3A shows the shielding layer in an enlarged illustration 30 / the adhesive layer 86, which is preferably designed as a carrierless adhesive film, the circuit board carrier 31, which is on conventionally applied copper track 88, where the Cross sections 88A and 88B e.g. B. already after etching still existing conductor tracks of the printed circuit of the formerly complete layer 88 indicate.

3 shows the section of the composite plate 87, but through 180 ° pivoted with respect to the installation position according to FIG. 5.

In Fig. 5 this composite board sits snugly in an annular edge 110 112 of the flange 27, and the inner surface of the F. (anscties has circumferentially distributed lugs 111 on which the composite board rests more or less snugly, the outer area of the composite board preferably before it is inserted same in the flange bottom surface 112 is provided with a noise-damping coating 113, so that flange 27, shielding ring 30 through this layer 113 forms a noise-dampening sandwich layer.

FIG. 4A shows an intermediate state in production, a single composite board unit 91 still hanging in here in the association of the large-area plate 92 according to FIG. 4B. The bridges in the area 94 are still present, so that only the sickle-shaped, z. B. four-part circular circumferential punchings 93 limit a composite board unit. The entire plate 92 is first built up in its various layers. Thereafter, the layer 88 is etched in accordance with FIG. 3A, so that the printed conductor tracks result. The recesses 93 are then punched out. Then the large-area plate 92 is placed on a placement machine for chip placement and then for manual placement with further components (which are not suitable for automated qgp placement) on the underside (see Fig. 3), i.e. on the surface of the circuit board carrier 31 The recesses 93, the central recess 95, and the recesses 96 and 97 are punched out with the sickle-shaped incisions 93 at the same time. After complete assembly, the individual units 91 are first punched out of the large-area composite circuit board 92 by punching the circumference of each unit 87 or 91 free around the bridges 94 only by punching punches, which are indicated in FIG. 4A.

In Fig. 1 or Fig. 5, the bearing support tube is held in one piece with the flange in a light metal die-cast design. The ball bearings 25 and 24 are arranged very compact axially. Between them and between the lower bearing 24 central flange part 13, which holds the outer rotor bell, v only a minimally necessary distance, which is still filled by spring spacer elements. The . extreme axial compactness reduces the bearing quality. Therefore, the lower ball bearing is provided as possible in the axial center of the laminated stator core and also in the axial center of the rotating permanent magnet ring 14 in order to ensure the smoothest possible run.

The disk storage hub 34 appears in the embodiment of FIG. 5 z. B. stronger in the flange 27, in this way increasing the axial compactness. The nested arrangement of the magnetic seal serves the same purpose 35 at the upper end of the bearing tube 23 is provided so that the disk hub is the bearing tube partially encompassed.

If you make the circuit board carrier, ie the layer 31 increasingly thinner and appropriate plastic, for. B. polyimides, the film can also be wrapped, possibly even folded over several times for greater spatial compactness. Because with a relatively small air gap diameter it can also be difficult be able to accommodate the components and the circuit in the ring area of Fig. 5. By bending and redirecting it, a greater use of space is possible.

The Hall generator 41, so the permanent motor magnet 14 and is acted upon by the index magnet 18, evaluates these two pieces of information about the Comparators 45, 46 according to FIG. 6 (see also application P 34 21 487.9) are different from, whereby the generation of the original signal is not necessarily via a Hall generator must take place. The generation of the pulse can e.g. B. also according to DE-OS 33 19 029 (DE-298) happen via an induction loop guided over two stator poles and this substitution of the pulse generation would then be dashed in FIG. 6 from that there Induction coil 141 shown (which is provided as a diameter winding on the stator is) performed (shown in detail in DE-OS 33 19 029). Then would have the resistances 78 and the internal resistances of the Hall generator 41 of FIG. 6 are infinite large values so that they would not exist in the circuit. The induction coil 141 (dashed coil) and the Hall generator 41 with the resistor 78 according to FIG. 6 there are alternative ways to generate the original signal.

If you look at the magnetic tracks of the index magnet 18 and the motor magnets 14 thinks completed, as shown in Fig. 7A, then sees the induction course in the axial area a of the permanent magnet, how it acts on the Hall generator (through Overlay of the index magnet 18 and the motor magnet 14) there as in 7B. So you have an applied, relatively sharp impulse I. on the trapezoidal induction blocks T (the latter from the motor magnet). That leads overall to a magnetic flux distribution over the circumference, as shown in Fig. 7C, namely running essentially triangular, but the "tips" are rounded. The stator has four salient poles opposite to the axis of rotation 100 mutable Distance between its outer pole surfaces and opposite the axis of rotation 100 cylindrical inner surfaces of the four permanent magnetic Sector shells 101, 102, 103, 104, which correspond to these four stator poles. the four stator poles are alternately wound in opposite directions and bifilar.

The Fig. 1, shown in double natural size, has a cube-shaped Index magnet 18 with an edge length of 2 mm made of samarium cobalt with a remanent Induction of 8-9 KG; the latter is radially magnetized (radial, i.e. perpendicular to the axis of rotation 100).

In the external rotor rotor bell 11 are four permanent quarter-shell magnets (as motor magnets 14) 101, 102, 103, 104 glued in. These four quarter-shell magnets have relatively small ones Pole gaps 108, which are distributed equidistantly on the circumference and offset by 900 to one another are. The pulse magnet 18 is now opposite a pole gap at an angle β of about 200 mech. offset against the direction of rotation (arrow 107). The distance to the pole gap 108 must be so large that the full amplitude value of the trapezoidal Magnetization at this point already exists in the air gap, thus the index pulse amplitude is fully added to this value. In practice it has been found that this is the case with a four-pole Rotor according to FIG. 8 at least 80 mech. should be. In this case you have 20 ° mech. chosen. In any case, a minimum distance ß from the pole gap must be maintained here 0 will.

An outer groove 105 (embossed or milled) enables an additional or alternative pulse generation. It is beneficial if this recess is in the middle a permanent magnet quarter shell (or half shell, depending on how large the polarity of the rotor) is because there the flow is to the left and divides right in the magnetic circuit so that in the center of the permanent magnet pole there is practically no field, and therefore this weakening or unbalancing of the Magnetic material there is of the least influence for a possible weakening of the Engine. For this reason, the angle 06 = 450 in FIG. 8. FIG. 8 shows a Natural size plan view of the open side of the housing rotor shell 11. This absolute size (air gap diameter approx. 45 mm) influences the possible solutions (compact arrangement in series production), also to a certain extent the size of the angle ß.

Claims (13)

Claims 9 Axially compact direct drive motor, as a brushless DC motor is designed with a permanent magnetic outer rotor to drive of signal processing devices, in particular so-called hard disk memories wherein the outer rotor is rotatably supported by a shaft in a bearing tube, and on this bearing tube a flange extends in a plane perpendicular to the bearing tube, wherein the outer rotor projects axially close to this flange and above it A plate hub is placed on the flange at the other end of the shaft and below of the flange, flat to the flange, a soft magnetic shielding ring around the center the bearing tube is provided, at least for a large part of its circumference, and that on this shielding a circuit board carrier with a printed circuit is attached, in that the shielding ring (30) and the circuit board carrier (31) through an adhesive layer (86) as a composite circuit board (87) is formed. 2. Axially compact direct drive motor according to claim 1, characterized in that g it is not noted that the adhesive layer is a linerless adhesive film (86) is trained. 3. Axially compact direct drive motor according to claim 1 and 2, characterized it is noted that the printed circuit board carrier (31) is a film made of polyester or polyimide is formed with a thickness of 0.5 mm or less. 4. Axially compact direct drive motor according to claim 3, characterized in that g It is not noted that the printed circuit board carrier (31) has a thickness of approximately 0.1 mm. 5. Axially compact direct drive motor according to one of the preceding Claims, characterized in that the composite board is essentially a has ring-shaped circuit board carrier (31) with printed circuit. 6. Axially compact direct drive motor according to claim 1 to 5, characterized it is noted that the composite board (87) has the winding heads of the inner stator (22) covers. 7. Axially compact direct drive motor according to one of claims 1 to 6, characterized in that the shielding ring (30) is at least partially rests flat on the flange. 8. The method for producing a composite board according to claim 1, in that the layer of the shielding ring (30) and of the circuit board carrier (31), which has a copper layer (88), intensively with one another are glued, then on such a large-area plate (92) of this composite material Individual circuits are often etched, then each. Single circuit (composite board unit (87)) by z. B. quarter, circular, sickle-like incisions (93) delimiting is punched around, but bridges (sQ) remain between these incisions and after loading the large-area plate (92) on a mounting machine as well as after manual assembly of further components on the individual circuit board carriers (31) of the composite board (87) these bridges (§4) are separated by punch. 9. The method according to claim 6, characterized g e k e n n z e i c h n e t that the gluing of the shielding ring (30) to the circuit board carrier (31) by means of linerless adhesive film under pressure and heat and / or under the action of solvents he follows. 10. Axially compact direct drive motor in particular according to claim 1, wherein the inner stator, preferably in a wide groove, has a Hall generator with four outputs, which is directed to the radial air gap field, in the vicinity of the rotor base, characterized in that the outer rotor (41) has a soft magnetic, deep-drawn, pot-like part, along whose inner hollow cylindrical wall circumferentially distributed permanent magnets axially to the inner surface of the pot bottom form a spacing space (118) which is axially covered at least at one circumferential point by a very small-volume remanent induction at least to a substantial extent 11. Axially compact direct drive motor according to claim 10, characterized in that g e k e n n z e i c h n e t that the index magnet (18) 1axially in the vicinity of the bottom surface, radially rests against a permanent magnet inside. 12. Axially compact direct drive motor according to claim 10 or claim 11, characterized in that the index magnet (48) is axially only slightly protrudes beyond the spacing space (118). 13. Axially compact direct drive motor according to claim 10, 11, 12, in that the axial length of the laminated stator core and the index magnet together is equal to that of the rotor magnet (14), preferably the axial center of the permanent magnet (rotor magnet 14) and that of the stator core lie roughly in one plane.